1. Field of the Invention
The present invention relates to a fog-resistant film which can be applied on plastic or glass substrates, and more particularly relates to a fog-resistant microporous SiOH film which can absorb water molecules by both the polar --Si--OH functional group and microporosity, and the method for manufacturing the SiOH film.
2. Description of Prior Art
Water vapor is easily condensed on both glass or plastic surfaces due to a thermal or moisture differential, thereby degrading the transparency and function of a lens made of glass or plastic. However, the above problem can be solved by coating a fog-resistant film on the surface of the lens.
There are, some different ways of forming a fog-resistant film in prior arts. For example, in U.S. Pat. Nos. 4,242,412, 4,332,859 and 5,075,133, they disclose a dipping method which coats a layer of high molecular-weight mixed film including many --C--OH functional groups on a substrate by dipping the substrate into the coating solution. Further, U.S. Pat. No. 4,214,908 describes a composite film of an inorganic salt and an ionic surface-active agent of long-chained molecular structure including a --SO.sub.3 base. Moreover, U.S. Pat. Nos. 4,478,909 and 5,134,021 provide a single layer or multiple layers of composite film including polyvinyl alcohol, silica nodules and organic silicon compound, the film generates a part of --Si--OH functional group after hydrolysis, therefore it has excellent anti-fogging ability. Another prior art is described in Application of plasma polymerization on ophthalmic lenses: equipment and processes'written by Christian Wohlrab et al. in OPTICAL ENGINEERING, Sep. 1995, Vol. 34, No. 9, which discloses a polymer anti-fogging film including --C.dbd.O and --C--OH functional groups incorporated on ophthalmic lenses by plasma polymerization.